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Vertical Deflection
The purpose of this stage is to:
¨ Manufacture a 60Hz vertical sawtooth signal to drive the yoke for verti-
cal (downward) beam deflection.
¨ Synchronize the vertical drive signal to the station's vertical frequency.
¨ Monitor the output signal for linearity correction.
¨ Immediately stop horizontal drive and have the TV shut down if there is
a loss of vertical output signal.
This vertical deflection stage consists of two signal paths:
1. The vertical output
2. The vertical feedback
Vertical Output
There are only a few stages of drive operation to make and amplify the
vertical signal to drive the deflection yoke. The yoke creates the magnetic
field to move the electron beam downward at a 60 Hz rate.
V e rtic a l S ig n a l to th e D e fle c tio n Y o k e
D e v ic e
In p u t
D ig ita l
+ 5 V – p in s 3 4 , 4 3
D e fle c tio n
S ta tio n s y n c
C o n tro l
S a m p le o f th e o u tp u t
IC 1 3 0 5
s ig n a l
V e rtic a l
D iffe re n tia l in p u t -
O u tp u t
p in s 1 a n d 7 .
IC 7 0 0 3
B o o s t v o lta g e – p in 6 .
O u tp u t
P u rp o s e
V D +
W h e n + 5 V p o w e r is
/p in 2 1
a p p lie d , s a w to o th
s ig n a l is o u tp u t.
V D -
/p in 2 2
S a m p le o f th e o u tp u t
s ig n a l is re tu rn e d fo r
fre q u e n c y a n d
lin e a rity c o rre c tio n
a n d p ro o f o f a ctiv ity.
V e rtic a l
C u rre n t a m p lifie r to
s a w to o th
d riv e th e lo w
o u tp u t a t
im p e d a n c e y o k e .
p in 5 .
M a k e s its o w n b o o s t
v o lta g e u s e d d u rin g
v e rtic a l re tra c e tim e .
85
When +5V is applied, the vertical drive signal is made in IC1305 and output
as an out-of-phase signal pair from pins 21 and 22. Each signal output is
2Vp-p.
The differential (out of phase) output signals are sent on long signal runs
(to a different board) to take advantage of common mode rejection. When
the same interference is picked up on both signal lines, one line can be
inverted and added to the other to cancel the noise. The output signal level
is added since they were originally complementary.
The vertical output IC7003 gets sufficient current from the +15V supply to
amplify the 2Vp-p input signal to 70Vp-p and drive the low impedance (12.1
ohms) yoke. The following output waveform shows the yoke's drive and
return voltage.
c h 1
c h 2
W a v e f o r m V D – V e r t ic a l Y o k e s ig n a l
N a m e
C h a n n e l 1
V e r t O u t p u t
C h a n n e l 2
V e r t r e t u r n
T im e b a s e
IC7003 Flyback Generation
The vertical output signal is 60Vp-p from IC7003, but the supply voltage is
only +15Vdc. Examination of the output waveform (ch 1) shows that only
the large retrace spike exceeds the 30-volt supply voltage.
The supply voltage necessary to meet the need during the retrace interval
(when there is a large spike) comes from a "flyback generator" within
IC7003. IC7003's flyback generator first uses the retrace portion of the
input signal to make a 0.5msec pulse, then amplifies it to 30Vp-p (supply
P M 3 3 9 4 , F L U K E & P H I L I P S
c h 1 : p k p k = 7 1 . 3 V
c h 2 : p k p k = 2 . 4 5 V
T
1
2
C H 1 ! 2 0 . 0 V =
C H 2 ! 1 . 0 0 V =
M T B 5 . 0 0 m s
c h 1 +
L o c a t io n
C N 4 0 0 2 / p in 6
C N 4 0 0 2 / p in 5
5 m s e c / d iv
V o lt a g e / d iv
6 0 V p - p
2 . 4 5 V p - p
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